Acidic copper electroplating baths and method



United States Patent O 3,400,059 I ACIDIC COPPER ELECTROPLATING BATHS AND METHOD Gregor Michael, Dusseldorf, and Wolf-Dieter Willmund, Dusseldorf-Holthausen, Germany, assignors to Dehydag Deutsche Hydrierwerke G.m.b.H., Dusseldorf, 'Germany, a corporation of Germany N Drawing. Filed Jan. 6, 1965, Ser. No. 423,822 Claims priority, applicatio; Germany, Mar. 7, 1964,

22 Claims. 61.20442 ABSTRACT OF THE DISCLOSURE Method and electrolyte for copper plating in which the leveling agent in the electrolyte is a compound of the formula PRIOR ART It is known to add to acid electroplating baths, as brightening agents, those organic sulfonic acids or their salts, which possess in the molecule at least one thiourea radical and at least one dithiocarbamic acid radical. These impart simultaneously leveling properties to the baths admixed with same. As in other known leveling agents for acid copper baths, the leveling characteristic is elfective only in those baths, whose chlorine-ion concentration does not essentially exceed 60 mg./l. But as a large part of the tap waters used nowadays already is higher in its chlorineion content, due to chlorine treatment, all leveling results in acid copper baths, prepared with such tap waters, has been insufiicient to the present time. A chlorine-ion content of about 20 to 60 mg./l. is considered normal and as r a rule does not cause any appreciable disturbances even in its upper range. However, as soon as the chlorine content is increased, very significant losses of the leveling effect may occur.

OBJECTS OF THE INVENTION It is, therefore, an object of this invention to provide an acid copper electroplating process and bath providing level electrodeposits in the presence of high chlorine-ion content.

A further object is to provide additives for an acid copper electroplating process and bath whereby level electrodeposits may be obtained when using ordinary tap water.

These and other objects of our invention will become apparent as the description thereof proceeds.

THE INVENTION It has been discovered, that acid electroplating copper baths with a high chlorine-ion concentration above 60 mg./l. which possess normally a relatively low equalization effect, furnish markedly leveled copper precipitates when organic compounds are added to these baths, these compounds possessing a thiourea radical and a dithiocarbamic acid radical in the grouping NHC NH-C H2SCN/ wherein the free valences of the nitrogen atoms may be bound to aliphatic, cycloaliphatic or aromatic radicals or hydrogen, wherein the free valences of the nitrogen atom of the dithiocarbamic acid radical, together with the nitrogen may also form a hetero ring system, and wherein the free valence of the nitrogen atom of the thiourea radical may also be bound to another dithiocarbamic acid 4- met-hylester radical according to the formula above.

More specifically, the compounds used in the baths have the formula wherein R and R are selected from the group consisting of hydrogen, alkyl, cycloaliphatic, aromatic and together with N an aromatic heterocyclic residue, and R is selected from the group consisting of hydrogen, alkyl, cycloaliphatic aromatic and the group as above defined.

Examples for compounds of the type to be used according to the invention, which contain the grouping indicated above, are as follows:

The compounds used according to the invention may be prepared in a simple manner according to methods well known. They may be combined in the acid electroplating copper baths with the usual additives, especially with brightening agents. Especially satisfactory brightening agents have proven to be compounds which have at least one carbon atom exclusively surrounded by hetero atoms, to which a bivalent aliphatic or aromatic radical,

containing an endpositioned sulfonic acid group, is bound through sulfur or nitrogen, which are known in the art. Particularly favorable results may be obtained when those organic sulfonic acids or their salts are used as brightening agents which possess in the molecule at least one thiourea radical and at least one dithiocarbamic acid radical, as described in copending application United States Ser. No. 170,522, filed Feb. 1, 1962, now Patent No. 3,203,878.

Of all leveling agents used according to the invention, the N,N-diethyl-thiocarbamylmercaptomethyl-N'-phenylthiourea (compound No. 5) presents the best results in customary baths with high chlorine-ion concentration as well as in those which contain the specific brightening agents indicated above.

The leveling agents used according to the invention are added in quantities of 0.001 to 20 g./l., preferably of 0.01 to 0.5 g./l. of bath liquor. The brightening agents, considered as especially favorable for the combination, are added in a quantity of 0.05 to 5 g./l., preferably 0.1 to 0.5 g./l. of bath liquor. The copper-plating process is conducted in the generally customary temperatureand current density ranges.

The following specific examples are presented to illustrate the invention and to enable persons skilled in the art to better understand and practice the invention and are not intended to be limitative.

Example I l g./l. of the addition product of 13 mol of ethylene -mercapto-methyl-N-phenyl-thiourea with propansultone Example IV 0.4 g./l. of the reaction product of N,N-dietl1yl-thiocarbamyl-mercaptornethyl-N-phenylthiourea with propansultone were added to an acid copper bath of the same basic composition as in Example I.

The bath was air agitated and furnished within the temperature range of 10 to 35 C. a satisfactory leveling at a low chlorine-ion concentration of 20 to 50 mg./l. But in comparison to this only a moderate leveling was obtained at a high chlorine-ion concentration of about 280 mg./l., with unvaried brightness effect. By additions of 0.06 to 0.08 g./l. of the compounds No. 3 or No. 5, the satisfactory leveling ability even at the high chlorine-ion concentration was restored again Example V An air agitated copper bath of the basic composition as in Example I with an addition of 0.08 g./l. of the Nasalt of the diethyldithiocarbamic acid propyl ester sulfonic acid as a brightening agent and l g./l. of N,N,N', N-tetrabu'tyl-1,3-diaminoisopropanol, which has a chlorine-ion concentration of 260 mg./l., furnished at 20 to C. at a current density range of 1 to 8 amp/dm.

were added to an acid copper plating bath of the basic combination of 210 g./l. copper sulfate and 60 g./l. of sulfuric acid, as a brightening and leveling agent. This bath furnished ductile copper plates free from pores, of high uniform brightness and well leveled, at a chlorine-ion content of 20 to 60 mg./l. and a temperature tolerance of 10 to C. in a current density range of 0.5 to 8 amperes/ dm.

However, if this bath is brought to a chlorine-ion concentration of 230 mg./l., the leveling effect of the bath is lost to an extensive degree. With an addition of 0.06 g. per liter of bath fluid of N,N-diethyl thiocarbamyl-mercapto-methyl-N-phenylthiourea (compound No. 5) the leveling effect of the bath is completey restored.

Example 11 1 g./l. of the addition product of 18 mol of ethylene oxide to 1 mol of nonephenol as a wetting agent, 0.25 g./l. of the reaction product of N,N-bis-(diethyl-thiocarbamyl-mercaptomethyl)-thiourea with propansultone as a brightening agent and 0.1 g./l. of the compound No. l were added to an acid copper plating bath of the same composition as in Example I having a chlorine-ion concentration of 250 mg./l. The bath furnished, at a temperature tolerance of 10 to 35 C. in the current density range of 0.5 to 8 amp/dm. ductile copper platings, free from pores and satisfactorily leveled and of an excellent high luster. When compound No. 1 was omitted in this bath, the leveling effect of the bath was lost to a substantial extent. If, on the other hand, an elementary bath with 20 to 50 mg./l. of chlorine-ion concentration was used, no supplementary addition of compound No. 1 was needed to produce a satisfactory leveling.

Example III 1 g./l. of the addition product of 18 mol of ethylene oxide in 1 mol of nonylphenyl as a wetting agent and 0.1 g./l. of the reaction product of N,N-dicthyl-thiocarbamylductile, pore-free glossy copper precipitates, which were not leveled, however.

But, when 0.06 to 0.1 g./l. of the compound No. 5 was added to the bath of the composition described above, a bath was obtained having simultaneously good leveling ability and furnishing ductile, pore-free copper deposits of a high luster and satisfactorily leveling.

While certain specific exampes and preferred modes of practice of the invention have been set forth it will be understood that this is solely for the purpose of illustration and that various changes and modifications may be made without departing from the spirit of the discosure and the scope of the appended claims.

We claim:

1. An acid copper electroplating bath for obtaining level electrodeposits comprising an aqueous solution of an inorganic copper salt and having a chlorine-ion concentration above 60 mg./l., containing as a leveling additive from 0.001 to 20 g./l. of an organic compound, of the formula S S R1 wherein R and R are selected from the group consisting of hydrogen, alkyl, cycloaliphatic, aromatic and together with N an aromatic heterocyclic residue and R is selected from the group consisting of hydrogen, alkyl, cycloaliphatic, aromatic and the group as above defined.

2. The bath of claim 1, which further contains compounds as brightening agents having at least one carbon atom exclusively surrounded by hetero atoms, a member 5 selected from the group consisting of a bivalent aliphatic and aromatic radical with a sulfonic acid group being bound to said'carbon atom through a member selected from the group consisting of sulfur and nitrogen.

' 3. The bath of claim 1,.acontaining as brightening agents, organic sulfonicacids and their salts, having in the molecule at least one thiourea group and at least one dithiocarbamic acid group.

4. The bath of claim 1 wherein the leveling additive is 1 '-C2H5 Q NHCNHCIIz-SCN H II S S (4H5 5. The bath of claim 1 wherein the leveling additive is C2115 CzHs /NC S--CHzNHfi-NH-CHzS-CN C9115 S S S \C2H5 6. The bath of claim 1 wherein the leveling additive is CHr-CH:

1' 5 s2 CIIr-CH:

7. The bath of claim 1 wherein the leveling additive is CHe-CHa CHZ-CHfl N(|f-SCHz-NH([%-NHCHa-S"El-N /NH CHTCHZ s s s CI'Ii-CHI 8. The bath of claim 1 wherein the leveling additive is CHz-CH2 C2115 CH1 /CHNHfiNHOH-SQ-N oHz-o'rn s s C2Hn 9. The bath of claim 1 wherein the leveling additive is NH2C-NH-CH2SCN II I! S OH:

10. The bath of claim 1 wherein the leveling additive is NHz(|fNH-CH:S(||JNH2 s s 11. An acid copper electroplating bath for obtaining level electrodeposits comprising an aqueous solution of an inorganic copper salt and having a chlorine-ion concentration above 60 mg./l., containing as a leveling additive from 0.01 to 0.5 g./l. an organic compound of the formula wherein R and R are selected from the group consisting of hydrogen, alkyl, cycloaliphatic, aromatic and togetherwith N an aromatic heterocyclic residue and R is selected from the group consisting of hydrogen, alkyl, cycloaliphatic, aromatic and the group NOSCH;- ll R1 s as above defined.

12. A process for obtaining level copper electrodeposits from an acid copper electroplating bath comprising an aqueous solution of an inorganic copper salt and having a chlorine-ion concentration above 60 mg./l., containing as a leveling additive from 0.001 to 20 g./l. of an organic compound, of the formula R RzNH(IIJNHCHzS(FIN wherein R and R are selected from the group consisting of hydrogen, alkyl, cycloaliphatic, aromatic and together .with N an aromatic heterocyclic residue and R is selected from the group consisting of hydrogen, alkyl, cycloaliphatic, aromatic and the group /NCSCH- R1 S as above defined.

13. The process of claim 12, which further contains compounds as brightening agents havin at least one carbon atom exclusively surrounded by hetero atoms, a member selected from the group consisting of a bivalent aliphatic and aromatic radical with a sulfonic acid group being bound to said carbon atom through a member selected from the group consisting of sulfur and nitrogen.

14. The process of claim 12, containing as brightening agents, organic sulfonic acids and their salts, having in the molecule at least one thiourea group and at least one dithiocarbamic acid group.

15. The process of claim 12, wherein the leveling additive is 16. The process of claim 12 wherein the leveling additive is 17. The process of claim 12 wherein the leveling additive is 18. The process of claim 12 wherein the leveling additive is 19. The process of claim 12 wherein the leveling additive is our-on, out CHNH(!?NH-CHSCIN 20. The process of claim 12 wherein the leveling additive is S OH:

21. The process of claim 12 wherein the leveling additive is H s a,

7 wherein R and R are selected from the group consisting of hydrogen, alkyl, cycloaliphatic, aromatic and together with N an aromatic heterocyclic residue and R is selected from the group consisting of hydrogen, alkyl, cycloaliphatic, aromatic and the group as above defined.

References Cited UNITED STATES PATENTS 3,122,549 2/1964 Giindel 20452 XR 3,276,979 10/ 1966 Strauss et a1 20452 XR 2,910,413 10/1959 Strauss et a1. 204-52 X 3,203,878 8/1965 Willmund et a1. 20452 JOHN H. MACK, Primary Examiner.

10 G. KAPLAN, Assistant Examiner. 

